Method for determining the oxygen concentration O2 in a gas flow

Abstract

Embodiments for determining oxygen concentration using an oxygen sensor are provided. In one example, a method for determining oxygen concentration O2 in a gas flow of an internal combustion engine which is equipped with an engine controller and an oxygen sensor comprises determining the oxygen concentration O2,sens of the gas flow in a ceramic measurement cell of the sensor by current ISens which is detected by measurement and which flows when a constant voltage USens is applied and maintained, and correcting the oxygen concentration based on a pressure pSens at the measurement cell. In this way, the measured oxygen concentration may be corrected based on the pressure of the air at the sensor.

The invention claimed is: 
     
       1. A method for determining oxygen concentration O 2  in a gas flow of an internal combustion engine which is equipped with an engine controller and an oxygen sensor, comprising:
 determining an oxygen concentration O 2,sens  of the gas flow in a ceramic measurement cell of the oxygen sensor by current I Sens  which is detected by measurement and which flows when a constant voltage U Sens  is applied and maintained; 
 correcting the determined oxygen concentration based on a pressure p Sens  at the measurement cell; and 
 if exhaust gas recirculation (EGR) is enabled, adjusting an opening of an EGR valve coupled to a low pressure EGR line based on the corrected oxygen concentration. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the pressure p Sens  is detected by measurement via a pressure sensor. 
     
     
       3. The method as claimed in  claim 1 , wherein the pressure P Sens  is determined mathematically by a model. 
     
     
       4. The method as claimed in  claim 1 , wherein correcting the determined oxygen concentration further comprises correcting the determined oxygen concentration based on a variation of sensitivity of the oxygen sensor. 
     
     
       5. The method as claimed in  claim 4 , wherein correcting the determined oxygen concentration further comprises correcting the determined oxygen concentration based on a dimensionless factor C adap , with which the variation of the sensitivity of the oxygen sensor is compensated. 
     
     
       6. The method as claimed in  claim 5 , wherein correcting the determined oxygen concentration further comprises correcting the determined oxygen concentration based on a predefinable reference pressure p 0 , the determined oxygen concentration O 2,sens  provided as an output signal by the oxygen sensor, and a pressure factor K p  with which a deviation of pressure p Sens  from the reference pressure p 0  is compensated. 
     
     
       7. The method as claimed in  claim 6 , wherein the factors C adap  and K p  are determined during calibration by the engine controller. 
     
     
       8. The method as claimed in  claim 7 , wherein the calibration is carried out in an operating state of the internal combustion engine in which a corrected oxygen concentration O 2,cor  in the gas flow is known. 
     
     
       9. The method as claimed in  claim 8 , wherein the calibration is carried out when the corrected oxygen concentration O 2,cor  in the gas flow corresponds to an oxygen concentration O 2,atm  in ambient air. 
     
     
       10. The method as claimed in  claim 9 , wherein the calibration is carried out in an overrun mode of the internal combustion engine. 
     
     
       11. The method as claimed in  claim 10 , wherein the calibration is carried out n working cycles after the internal combustion engine starts the overrun mode. 
     
     
       12. The method as claimed in  claim 11 , wherein, to carry out the calibration, value ranges for the factors C adap  and K p  are predefined. 
     
     
       13. A system for an engine, comprising:
 an oxygen sensor including:
 a ceramic measurement cell; 
 a pressure sensor for measurement of a pressure p Sens  at the ceramic measurement cell; and 
 
 an engine controller including instructions to:
 apply a constant voltage U Sens  to the ceramic measurement cell; 
 while applying the constant voltage U Sens  to the ceramic measurement cell, measure a current I Sens  flowing in the measurement cell to determine an oxygen concentration O 2  of a gas flow of the engine; 
 measure the pressure p Sens  at the ceramic measurement cell with the pressure sensor; 
 correct the determined oxygen concentration based on the pressure measurement; and 
 adjust an exhaust gas recirculation (EGR) valve in response to the corrected oxygen concentration. 
 
 
     
     
       14. The system as claimed in  claim 13 , wherein a temperature sensor is provided at the ceramic measurement cell, and wherein the EGR valve is coupled to a low pressure exhaust gas recirculation (LP EGR) system. 
     
     
       15. The system as claimed in  claim 13 , wherein the oxygen sensor is provided in an intake system of the engine, wherein the intake system is equipped with a compressor of an exhaust-gas turbocharger and with a charge-air cooler arranged downstream of the compressor, and wherein the oxygen sensor and the pressure sensor are arranged between the compressor and the charge-air cooler. 
     
     
       16. A system, comprising:
 a supercharged engine including an LP-EGR system and an HP-EGR system, and an LP-EGR valve; 
 an oxygen sensor coupled in an intake of the engine; 
 an intake pressure sensor; and 
 a controller with non-transitory instructions stored in memory correcting a measured intake air oxygen concentration with at least a measured pressure of intake air and, if the LP-EGR system is enabled, adjusting the LP-EGR valve based on the corrected measured intake air oxygen concentration. 
 
     
     
       17. The system of  claim 16 , wherein the instructions further include instructions for:
 if the HP-EGR system is enabled, adjusting an HP-EGR valve based on estimated HP-EGR flow; and 
 if only the LP-EGR system is enabled, adjusting a fuel injection amount based on the measured pressure of the intake air to maintain a desired combustion air-fuel ratio. 
 
     
     
       18. The system of  claim 17 , wherein correcting the measured intake air oxygen concentration further comprises correcting the measured intake air oxygen concentration based on a pressure factor and a variation factor. 
     
     
       19. The system of  claim 18 , wherein correcting the measured intake air oxygen concentration based on the pressure factor and the variation factor further comprises setting the pressure factor and the variation factor during select conditions including known intake air oxygen concentration. 
     
     
       20. The system of  claim 19 , wherein the select conditions comprise deceleration fuel shut-off.